Some plausibly necessary a posteriori theoretical claims include ‘water is H 2 O’, ‘gold is the element with atomic number 79’, and ‘cats are animals’. In this paper I challenge the necessity of the third claim. I argue that there are possible worlds in which cats exist, but are not animals. Under any of the species concepts currently accepted in biology, organisms do not belong essentially to their species. This is equally true of their ancestors. In phylogenetic systematics, monophyletic clades (...) such as the animal kingdom are composed of an ancestral stem species and all of its descendants. If the stem species had not existed, neither would the clade. Thus it could have been the case that all the organisms which actually belong to the animal kingdom might have existed yet not have been animals. (shrink)

Animalism is prima facie the most plausible view about what we are; it aligns better with science and common sense, and is metaphysically more parsimonious. Thought experiments involving the brain, however, tend to elicit intuitions contrary to animalism. In this paper, I examine two classical thought experiments from the literature, brain transplant and cerebrum transplant, and a new one, cerebrum regeneration. I argue that they are theoretically possible, but that a scientifically informed account of what would actually happen shows that (...) in none of the cases would the person be separated from the animal. Our intuitions in these cases, when adequately informed by neuroscience, do not conflict with animalism – rather, they suggest a correction of the animalist position: the persisting animal should be at least minimally sentient. Sentience animalism is a new formulation of the animalist account of personal identity that allows us to reconcile facts about our biological persistence conditions with the intuition that human persistence should involve some kind of psychological continuity. (shrink)

Life on Earth descends from a common ancestor. However, it is likely that there are other instances of life in the universe. If so, each abiogenesis event will have given rise to an independently originated life clade, of which Earth-life is an example. In this paper, I argue that the set of all IOLCs in the universe forms a Darwinian population subject to natural selection, with more widely dispersed IOLCs being less likely to face extinction. As a result, we should (...) expect that, over time, more planets will become inhabited by fewer, more successful IOLCs. (shrink)